docs: def get_os_version_codename(codename, version_map=OPENSTACK_CODENAMES):
      '''Determine OpenStack version number from codename.'''
      for k, v in six.iteritems(version_map):
          if v == codename:
              return k
      e = 'Could not derive OpenStack version for '\
          'codename: %s' % codename
      error_out(e)